You've met pectin's one personality flaw. The moment a grain of pectin touches liquid, its outer layer hydrates INSTANTLY into a gel skin - sealing dry powder inside. Each evil pearl is a gel jacket with raw pectin trapped in the middle, and no amount of whisking gets through.
The rule, permanent and non-negotiable: mix pectin with a portion of the recipe's SUGAR first, dry, whisked well. The sugar grains physically separate the pectin grains, so when the mix rains into the liquid (gradually, stirring continuously) every pectin particle hydrates alone. Zero lumps, full setting power.
This applies to every pectin type and survives every substitution - even if your fruit base is pre-sweetened, hold back a spoon of sugar purely as the pectin's chaperone. Batch two will behave 🍓